The Bell X-1, originally designated XS-1, was a supersonic research project and the first aircraft to exceed the speed of sound in controlled, level flight. This resulted in the first of the so-called X-planes, an American series of experimental aircraft designated for testing of new technologies and usually kept highly secret.

Photos of the Bell XS-1 (X-1)The rocket-powered X-1 was launched from a B-29 "Mother ship"
Chuck Yeager, first man to break the sound barrier in level controlled flight
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In March 1945, the United States Army Air Forces' Flight Test Division and the National Advisory Committee for Aeronautics (NACA) (now NASA) contracted Bell Aircraft to build three XS-1 (for "Experimental, Supersonic") aircraft to obtain flight data on conditions in the transonic speed range. The XS-1 was the first high-speed aircraft built purely for aviation research purposes and was never intended for production.

The X-1 was a "bullet with wings" that closely resembled the shape of the Browning .50-caliber machine gun bullet that was known to be stable in supersonic flight. The pattern shape was followed to the point of seating the pilot behind a sloped, framed window inside a confined cockpit in the nose. The rocket propulsion system was developed in part by Dr.Robert Goddard, the "Father of American Rocketry." Eventually, the plane acquired movable tail surfaces and broke the sound barrier with Chuck yeager at the controlst in March, 1947 -- a remarkable job of anticipation by Jo Kotula who created the cover art in January of 1947 and had it run on the March, 1947 issue.